While I was researching substrates, I found that there wasn't a whole ton of information about Flourite Dark. I decided to go with it in my 10 gallon mostly as an experiment, and since I have some pictures I decided to post them up.
Unfortunately I don't have any pictures of the cleaning process, partly because I forgot until part way through, and partly because my computer is broken so I don't have access to the pictures I already took off my camera.
My method for cleaning was as follows:
1) Dump half a bag in a 4-gallon bucket
2) Fill bucket halfway with water, gently scoop under the substrate several times with my hand to stir up loose particles. Dump out water
3) Repeat step 2 ten times.
4) Dump out the flourite on a towel, spread thin, and let dry completely, as per lauraleellbp's suggestion.
Here's a picture immediately after I added water (see the plate?
) There was NO clouding, so either I was lucky, or this method works really well!
Here is a picture after I scraped all the bubbles off the sides. No clouding
These pictures give you an idea of grain size and color variation. There is a noticeable amount of color variations, but I don't think it looks bad. I'm partial to the black substrates myself, but I think this one looks pretty natural.
Unfortunately, the only other substrate I've used to date has been small round pebbles, so I can't compare to other planted tank substrates. I assume that it's fairly similar to flourite and flourite black in everything but color. Having a pair of forceps really helps with planting, as it's hard to get stems in deep enough with just your fingers (without digging a bigger hole than you need)
The color is more red than I thought it would be; it's definitely a reddish-brown, not a brown brown. Here are some pictures after my preliminary plantings.
The shade in these pictures is pretty good, for showing the darkness, although the tone is a little more purple (less red) than real life.
I hope this info is helpful!